The approaches described in this section could be pursued, but are not necessarily approaches that have been previously conceived or pursued. Therefore, unless otherwise indicated herein, the approaches described in this section are not prior art to the claims in this application and are not admitted to be prior art by inclusion in this section.
The recurring outbreak of message-borne viruses in computers linked to public networks has become a serious problem, especially for business enterprises with large private networks. Direct and indirect costs of thousands of dollars may arise from wasted employee productivity, capital investment to buy additional hardware and software, lost information because many viruses destroy files on shared directories, and violation of privacy and confidentiality because many viruses attach and send random files from a user's computer.
Further, damage from viruses occurs over a very short time period. A very high percentage of machines in an enterprise network can be infected between the time that the virus breaks out and the time virus definitions are published and deployed at an enterprise mail gateway that can detect and stop virus-infected messages. The window of time between “outbreak” and “rule deployment” is often five (5) hours or more. Reducing reaction time would be enormously valuable.
In most virus outbreaks, executable attachments now serve as a carrier of virus code. For example, of 17 leading virus outbreaks in the last three years, 13 viruses were sent through email attachments. Twelve of the 13 viruses sent through email attachments were sent through dangerous attachment types. Thus, some enterprise network mail gateways now block all types of executable file attachments.
Apparently in response, virus writers are now hiding executables. Increasingly, virus writers are hiding known dangerous file types in files that appear to be innocent. For example, a virus writer may embed executables within .zip files of the type generated by WinZIP and other archive utilities. Such .zip files are very commonly used by enterprises to compress and share larger files, so most enterprises are unwilling or unable to block .zip files. It is also possible to embed executables in Microsoft Word and some versions of Adobe Acrobat.
Based on the foregoing, there is a clear need for an improved approach for managing virus outbreaks. Present techniques for preventing delivery of mass unsolicited commercial email (“spam”) and messages that contain other forms of threats, such as phishing attacks, are also considered inadequate. Present techniques for scanning messages for threats are also considered inefficient and in need of improvement.